Ashfork-Bainbridge Steel Dam

The Ashfork-Bainbridge Steel Dam was constructed by the Atchison, Topeka & Santa Fe Railway to provide a steady water supply in Arizona.

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The Ashfork-Bainbridge Steel Dam, the first large steel dam in the world, and one of three built in the United States, was constructed in 1898 by the Atchison, Topeka and Santa Fe Railway (ATSF) to supply water for railway operations near Ash Fork, Arizona.

The dam has been listed on the National Register of Historic Places since 1976 and is an Arizona Historic Civil Engineering Landmark..

History

Proposal

In the late 19th century, the ATSF faced the challenge of supplying water to its steam-powered locomotives in the arid northern Arizona desert. Non-condensing steam locomotives consumed large amounts of water, and railroads commonly addressed this need by constructing dams to capture surface runoff or by drilling wells and storing water in tanks. ² Settlements often developed around these water stops. Ash Fork had served as such a location since the arrival of the ATSF, though it had earlier been a waypoint for regional stagecoach lines. ^{4 [88]}

Beginning in 1894, the Santa Fe built a series of dams and reservoirs near Ash Fork to provide a dependable water supply. The first three were conventional masonry structures. In 1897, however, ATSF engineer Francis H. Bainbridge proposed constructing the fourth dam from steel rather than stone. ^{1 6} The site was difficult to access with heavy masonry materials, but prefabricated steel beams and plates could be transported more easily by rail. The proposal was accepted, and Bainbridge worked in collaboration with James Dun, the Santa Fe’s chief engineer, to develop the design. ⁶

By this period, railroads in the United States and abroad had been leaders in structural innovation, replacing masonry arch bridges with steel designs that offered reduced material costs, faster construction, and improved efficiency. ^{3 [124]} Bainbridge believed these same advantages could be applied to dam construction, simplifying logistics and reducing labor demands compared to quarrying and setting stone. ^{1 6}

Design Principles

Bainbridge and Dun designed the Ash Fork Steel Dam as a buttress dam with an inclined upstream face, a form similar to some timber-frame dams of the 19th century. The structure’s central 184-foot-long section was made of steel, while its shallow wing sections used conventional masonry construction to complete a total crest length of 300 feet. ^{3 [125]} The steel section was supported by 24 triangular bents, or frames, made from I-beams and spaced eight feet apart. ^{1 5} At a 45° slope, the bents carried ⅜-inch-thick curved steel plates, with their concave surfaces facing upstream. The curvature allowed for expansion and contraction due to temperature changes without stressing the riveted joints. The plates alternated between rigid and loosely connected types to accommodate an annual temperature range from 104 °F to −4 °F. ¹

Steel dams rely on relatively thin plates backed by a structural framework that transmits the water load to the foundation. In the Ash Fork design, the angled plates ensured that hydraulic pressure produced primarily compressive forces rather than bending stresses, reducing strain on the structural members. At the site, very hard igneous bedrock permitted the engineers to anchor the bents and toe of the dam directly into the rock, with some concrete used as a sealant.

Construction

The Ash Fork Steel Dam was fabricated by the Wisconsin Bridge & Iron Company and shipped in prefabricated sections to the site. ^{2 5} Santa Fe crews began work in October 1897 and completed the dam on March 5, 1898, at a cost of $63,519. The steel portion of the structure is 46 feet high and weighs approximately 460,000 pounds.

Notably, the dam was built without a spillway. ^{1 5} Instead, it was designed to withstand overtopping, allowing up to six feet of water to flow over its crest without damaging the structure. ¹ When full, the reservoir behind the dam holds an estimated 36 million gallons of water. ^{2 5}

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Gallery

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Sources

1. Bainbridge, F. H. Ashfork-Bainbridge Steel Dam. Historic American Engineering Record, HAER No. AZ-12, U.S. Department of the Interior, National Park Service, 1979. Library of Congress.
2. Culpin, Mary. Ashfork-Bainbridge Steel Dam. National Register of Historic Places Inventory–Nomination Form, National Park Service, 1976.
3. Wells, John. “Steel Dams in America: A Technological Rarity.” Journal of Engineering History, vol. 24, no. 2, 1993, pp. 121–136.
4. Smith, Richard K. The Santa Fe Railway in the Desert Southwest. University of New Mexico Press, 1980.
5. “Ash Fork Bainbridge Steel Dam.” Ash Fork Water Service.
6. Jackson, Donald C., editor. Dams. Taylor & Francis, 1997. eBook.